The invention relates to a vertical power semiconductor component, e.g. a vertical high-voltage diode, a GTO or a vertical IGBT (Insulated Gate Bipolar Transistor), in which there are formed, on the rear side of a substrate, a cathode or a cathode emitter or an anode or an anode emitter or a rear side emitter of an IGBT and, over that, a rear-side metal layer that at least partly covers the latter.
In the edge region of vertical power semiconductor components, such as diodes or IGBTs, dynamic effects, caused by free charge carriers may cause a significant reduction of the blocking capability in said edge region with respect to the ideal breakdown voltage and also with respect to the blocking capability of the active region during the turn-off operation. During the turn-off operation, it may happen, on account of the resulting increased charge carrier concentration in the regions of the edge or the drive terminals, that both the electric field strength in the silicon and the field strengths in SiO2 layers or further insulator layers which have been deposited on the silicon surface for the purpose of passivation or field plate formation in the edge region are greatly increased. By virtue of field strength spikes, an avalanche breakdown in the silicon or a breakdown of the oxide or of the insulator layer may occur there.
Instead of p-rings with field plates, it is also possible to use other edge constructions, such as with p-rings without field plates or VLD edges with an electroactive, semiinsulating or else insulating covering individually or in combination also with further edge terminations known per se. For all these edge terminations, the measures described lead to an improvement in the dynamic properties.
EP 0 419 898 describes methods which, in the case of thyristors, by means of a laterally inhomogeneous carrier lifetime setting, lower the concentration of free charge carriers in the edge region and thus increase the static and dynamic blocking capability of the thyristor. However, this procedure often requires a considerable process complexity and is thus expensive. Similar methods are used in the prior art in the case of diodes, too, for achieving a laterally inhomogeneous carrier lifetime.